Pre-Scaled Units Velocity is missing

[iltara]

I have just noticed that there is no pre-scaled velocity units; unfortunately there isn't also a "general" setting, so if the unit is not listed it is not possible to choose a general one. Is there any workaround?

Thanks in advance

Marco

[Norbert_B]

Marco,

what are you talking about? DAQmx?

Just a shot in the blue:

Pre-scaled units are voltage and current only. This is no surprise since transducers convert a physical phenomenon into voltage or current. That is being sampled by the DAQ device.

Scaling converts the voltage/current "back to the physical parameter". Scaling is done either linear, by table, by polynom or ranges.

An example:

1V represents 1g (acceleration)

2V represents 2g

If scaling is linear:

1.5V => 1.5g

hope this helps,

Norbert 

[Thoric]

Marco,

If you are talking about assigning units to the datatype, then a pre-scaled velocity is equivalent to having no units. If you want to use the units functionality of LabVIEW then you need a unit base that posesses scale to permit conversion between the various units. You can then use the Convert Unit Function to apply a unit and change between desired units.

[iltara]

Well, the point is to create a DAQmx scale for each channel that I am acquiring so that the output of the daqmx read is already the signal in EU. The DAQmx create scale polymorphic vi requires as input a string (scaled units) and a ring (pre-scaled units).

If I understood correctly, "scaled units" are used only in the unit conversion, so it is possible to set the pre-scaled units to "Voltage" for any AI/Voltage task (as suggested by Norbert) without getting any DAQmx error. Is it correct? 

[Thoric]

Unfortunately I'm not sure of that, try it and see?

[Norbert_B]

In general, it is suggested to configure the DAQmx task as such that it already fits the requirement.

So acquiring e.g. temperature using RTDs, you would configure an RTD task.

DAQmx already gives you plenty of scalings at hand.

Manual scaling is only necessary in special cases, and the settings depend on your task. Is it a voltage channel? So go for pre-scaled "voltage". Is it current? Go pre-scaled for current.

Is the scaled value force, go for N, kg*g or whatever derived format.... 

Norbert 

[Norbert_B]

Ah, ok, now i see what you are up to:

 

Is this the list where you miss velocity (m/s)?

Norbert 

[iltara]

Well that's true, but our situation is quite complex. We have about 30 different NI data acquisition boards, and I have created an acquisition software that allows their configuration without entering MAX. The best choice was creating a custom scale for each channel, to have the maximum flexibility. So I would't change this setup; i will try to see if the adoption of "voltage" works in any situation

[iltara]

To Norbert previous post, yes, it's this one. I am trying to compile my code to see if it works with all our DAQ boards

[Norbert_B]

Hm, you are right that velocity is obviously missing.

Nevertheless, some channels are not really suitable as voltage channels.

e.g. thermocouples (low, non-linear voltage) and externally supplied acquisitions like acceleration, force and strain.

To be precise: Certain acquistions have to use different settings in order to work.

That being said, most channels can be used as voltage channels and then "converted using scaling". But my feeling tells me that pre-scale only voltage will be used...

Norbert